What purpose does a hexblade have in a party?

[CyberThread]

what purpose does a hexblade fill in a party, the fighter role, or the secondary slots?

[Flickerdart]

A hexblade, as appropriate from a base class from Complete Warrior, is a fighter-type. His class features are intended to back up his fighting, not extend his scope into another roleslice.

[Nerd-o-rama]

A fighter who can throw some debuffs on the enemy and provide yet another fighter if he invests feats in his familiar.

[CyberThread]

whats the big risk of that fam ending up dead?

[Flickerdart]

It's less risky than for a sorcerer or wizard - a d10 hit die and full BAB make for a hearty pet. Still, half of your HP is not a lot of HP, so the familiar is best relegated to a hit and run combatant or wand user guy, rather than a melee buddy. The one exception is mounts - a large enough Improved Familiar is a very nice mount indeed, and with Ride-by Attacks and exotic movement modes you're likely to avoid too much retaliation.

[Mishkov]

what purpose does a hexblade fill in a party, the fighter role, or the secondary slots?

Fighter and making sure your wizard/cleric/druid/debuffer lands their spells.

Take dark companion ACF and obtain familiar if your DM allows it.